Acceleration sensor with redundant contact holes

Abstract

An acceleration sensor includes a mass and a supporting member linked by a flexible beam. A strain detector having low-resistance areas at both ends is formed near a boundary between the beam and the mass or between the beam and the supporting member A dielectric film formed on the supporting member and the beam has multiple contact holes disposed over each low-resistance area. Wiring formed on the dielectric film is connected to the low-resistance areas through the contact holes. The provision of multiple contact holes for each low-resistance area extends the life of the acceleration sensor by preventing sensor failure due to the separation or other failure of any single contact.

1. An acceleration sensor comprising:
 a mass; 
 a supporting member surrounding the mass; 
 a beam flexibly linking the mass to the supporting member; 
 a strain detector formed as a single continuous unit on the supporting member and the beam, the strain detector having a first end formed on the beam and a second end formed on the supporting member; 
 a dielectric film at least covering the strain detector, the dielectric film having a plurality of first contact holes disposed over the first end of the strain detector and a second contact hole disposed over the second end of the strain detector; 
 first wiring formed on the beam and in the first contact holes, making electrical contact with the strain detector; and 
 second wiring formed on the supporting member and in the second contact hole, making electrical contact with the strain detector. 
 
     
     
       2. The acceleration sensor of  claim 1 , wherein the dielectric film has a plurality of second contact holes disposed over the second end of the strain detector, said second contact hole being one of said plurality of second contact holes, and the second wiring is formed in the plurality of second contact holes, making electrical contact therethrough with the strain detector. 
     
     
       3. The acceleration sensor of  claim 1 , wherein the first contact holes have different sizes. 
     
     
       4. The acceleration sensor of  claim 1 , wherein the strain detector includes a low-resistance area and the first wiring makes electrical contact with the low-resistance area of the strain detector. 
     
     
       5. The acceleration sensor of  claim 1 , wherein the first contact holes are mutually aligned in a longitudinal direction of the beam. 
     
     
       6. An acceleration sensor comprising:
 a mass; 
 a supporting member surrounding the mass; 
 a beam flexibly linking the mass to the supporting member; 
 a strain detector formed as a single continuous unit on the mass and the beam, the strain detector having a first end formed on the beam and a second end formed on the mass; 
 a dielectric film at least covering the strain detector, the dielectric film having a plurality of first contact holes disposed over the first end of the strain detector and a second contact hole disposed over the second end of the strain detector; 
 first wiring formed on the beam and in the first contact holes, making electrical contact with the strain detector; and 
 second wiring formed on the mass and in the second contact hole, making electrically contact with the strain detector. 
 
     
     
       7. The acceleration sensor of  claim 6 , wherein the dielectric film has a plurality of second contact holes disposed over the second end of the strain detector, said second contact hole being one of the plurality of second contact holes, and the second wiring is formed in the plurality of second contact holes, making electrical contact therethrough with the strain detector. 
     
     
       8. The acceleration sensor of  claim 6 , wherein the first contact holes have different sizes. 
     
     
       9. The acceleration sensor of  claim 6 , wherein the strain detector includes a low-resistance area and the first wiring makes electrical contact with the low-resistance area of the strain detector. 
     
     
       10. The acceleration sensor of  claim 6 , wherein the first contact holes are mutually aligned in a longitudinal direction of the beam. 
     
     
       11. An acceleration sensor comprising:
 a mass; 
 a supporting member surrounding the mass; 
 a beam flexibly linking the mass to the supporting member, the beam being joined to the supporting member at a first boundary and to the mass at a second boundary; 
 a first strain detector formed as a single continuous unit on the supporting member and the beam, the first strain detector having a first end formed on the beam and a second end formed on the supporting member; 
 a second strain detector formed as a single continuous unit on the mass and the beam, the second strain detector having a first end formed on the beam and a second end formed on the mass; 
 a dielectric film at least covering the first strain detector and the second strain detector, the dielectric film having a plurality of first contact holes disposed over the first end of the first strain detector and a plurality of second contact holes disposed over the first end of the second strain detector; and 
 first wiring formed on the beam and in the first contact holes and the second contact holes, making electrical contact with the first strain detector and the second strain detector. 
 
     
     
       12. The acceleration sensor of  claim 11 , wherein the dielectric film has a third contact hole disposed over the second end of the first strain detector and a fourth contact hole disposed over the second end of the second strain detector, the acceleration sensor further comprising:
 second wiring formed on the supporting member and in the third contact hole, making electrical contact with the first strain detector; and 
 third wiring formed on the mass and in the fourth contact hole, making electrical contact with the second strain detector. 
 
     
     
       13. The acceleration sensor of  claim 11 , wherein the dielectric film has a plurality of third contact holes disposed over the second end of the first strain detector and a plurality of fourth contact hole disposed over the second end of the second strain detector, the acceleration sensor further comprising:
 second wiring formed on the supporting member and in the third contact holes, making electrical contact with the first strain detector; and 
 third wiring formed on the mass and in the fourth contact holes, making electrical contact with the second strain detector. 
 
     
     
       14. The acceleration sensor of  claim 11 , wherein the first contact holes have different sizes and the second contact holes have different sizes. 
     
     
       15. The acceleration sensor of  claim 11 , wherein the first strain detector includes a first low-resistance area and the first wiring makes electrical contact with the first low-resistance area of the first strain detector. 
     
     
       16. The acceleration sensor of  claim 11 , wherein the second strain detector includes a second low-resistance area and the first wiring makes electrical contact with the second low-resistance area of the second strain detector. 
     
     
       17. The acceleration sensor of  claim 11  wherein the first contact holes are mutually aligned in a longitudinal direction of the beam and the second contact holes are mutually aligned in the longitudinal direction of the beam.